Fix build problem with lib6 tests


Signed-off-by: Paul Larson <paul.larson@canonical.com>
---

diff --git a/testcases/network/lib6/Makefile b/testcases/network/lib6/Makefile
index 7c1784d..f622468 100644
--- a/testcases/network/lib6/Makefile
+++ b/testcases/network/lib6/Makefile
@@ -23,6 +23,10 @@
 CFLAGS+=	-I../../../include -g -D_GNU_SOURCE
 LOADLIBES+=	-L../../../lib runcc.a -lltp -lpthread
 
+ifeq ($(RANLIB),)
+RANLIB = ranlib
+endif
+
 SRCS=$(wildcard *.c)
 TARGETS= asapi_01 asapi_02 asapi_03 asapi_04 asapi_05 asapi_06 asapi_07 \
 	getaddrinfo_01 in6_01 in6_02